SUPPRESSION OF ERK ACTIVATION AND IN-VIVO GROWTH IN ESOPHAGEAL CANCER-CELLS BY THE DOMINANT-NEGATIVE RAS MUTANT N116Y

Our previous studies demonstrated that introduction of a dominant nega tive H-ras mutant, N116Y, inhibits the growth of various types of canc er cells in vitro. In this study, we tested the efficacy of N116Y in b locking the growth of esophageal cancer cells using an adenoviral vect or. Infection with N116Y adenovirus, (AdCMV-N116Y), in which N116Y exp ression is driven by the cytomegalovirus promoter, significantly reduc ed the in vitro growth of all esophageal cancer cell lines studied. Es ophageal cancer cells that contained wild-type K-ras and H-ras (TE8, S GF3, SGF7) were more sensitive to AdCMV-N116Y than HEC46 cells that ex pressed mutant K-ras protein. Most importantly, direct injection of Ad CMV-N116Y into TE8- or SGF3-induced tumors in nude mice suppressed the ir growth significantly. To examine the suppressive mechanism of N116Y , cell cycle profile and the activation of extracellular signal-regula ted kinase 2 (Erk2) were examined by flow cytometry and Western blot a nalysis, respectively. In TE8 cells, progression into S phase was clea rly blocked after infection with AdCMV-N116Y, Infection with AdCMV-N11 6Y did not strongly suppress the activation of Erk2 after EGF stimulat ion in serum-starved HEC46 cells, whereas it completely suppressed act ivation in TE8, SGF3 and SGF7 cells, Our observations suggest that N11 6Y reduces growth of human esophageal cancer cells and suppresses the activation of Erk2; they also indicate that N116Y is a potential candi date gene for human esophageal cancer gene therapy. int, J, Cancer 78: 366-371, 1998, (C) 1998 Wiley-Liss, Inc.